Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2006
Publication Date: 10/26/2006
Citation: Choi, S., Suh, B., Kozukue, E., Kozukue, N., Levin, C.E., Friedman, M. 2006. Analysis of the contents of pungent compounds in fresh korean peppers and pepper-containing foods. Journal of Agricultural and Food Chemistry.
Interpretive Summary: Solanum pepper plants synthesize secondary metabolites called capsaicinoids to protect themselves against phytopathogenic bacteria, fungi, and viruses. These compounds cause pungent, hot-tasting sensations when consumed as part of the diet. The major capsaicinoid called capsaicin is reported to possess biological properties that may affect human health. These include antibiotic effects against pathogenic microorganisms as well as against aquatic microorganisms that cause fouling of immersed surfaces of ships. As part of an effort designed to relate the structures of these compounds to antimicrobial effects against foodborne pathogens, we participated in a collaborative study carried out in Korea which demonstrated for the first time that HPLC can be used to simultaneously determine nine major and minor capsaicinoids in whole peppers and pepper-containing foods. The improved HPLC method merits further evaluation and use in studies designed define agronomic, food, forensic, and antimicrobial aspects of capsaicinoids. Biological properties of mixtures of capsaicinoids present in peppers remain largely unexplored.
Technical Abstract: Pepper fruits contain biologically active pungent compounds called capsaicinoids. We developed and validated an improved HPLC method for the concurrent analysis of extracts containing one unknown and up to eight of the following known capsaicinoids: capsaicin, dihydrocapsaicin, homocapsaicin-I, homocapsaicin-II, homodihydrocapsaicin-I, homodihydrocapsaicin-II, nonivamide, and nordihydrocapsaicin. HPLC was optimized by defining how composition of the mobile phase (acetonitrile/0.5% formic acid in H2O) affected retention times. Identification and quantification was based on retention times, the linearity of the UV response at 280 nm in HPLC, recoveries from spiked samples, and observed molecular ions of individual peaks in the mass spectra of the extracts determined by liquid chromatography/mass spectrometry (LC-MS). The method with a limit of detection of ~15-30 ng was used to quantify the distribution of capsaicinoids in 11 Korean whole peppers and in 12 commercial pepper-containing foods. Total capsaicinoid levels of whole peppers ranged from 1.21 'g/g for PR Gang ja variety to 121.1 for the Chung yang variety, a 100-fold variation from lowest to highest amounts. The levels in foods ranged from 11.0 'g/g for Radish Kimuchi to 4132.2 'g/g for Hot Chinese Noodles, an 86-fold variation from lowest to highest amounts. The results demonstrate the usefulness of the HPLC method for the simultaneous analysis of a wide range of capsaicinoids and offer consumers a choice of peppers and pepper foods containing very low to very high levels of capsaicinoids.